5. Stop valve
Regardless of the type of screw used, the tip is usually equipped with a stop valve. To prevent plastic from flowing out of the nozzle, a decompression (rewinding) device or a special shooting nozzle is also provided. If you use a stop-flow production and supply, you must check it regularly because it is an important part of the shooting tank. At present, switch-type nozzles are not commonly used because the nozzles are prone to leak plastic and break down. At present, each type of plastic has a suitable type of nozzle.
6. Screw back (rewinding)
Many injection molding machines are equipped with screw retracting or suckback devices. When the screw rotation is stopped, it is withdrawn by hydraulic pressure to suck back the plastic tip of the nozzle. This device allows the use of an open nozzle. The number of suckbacks may be reduced because entering the air can cause problems for some plastics.
7. Screw padding
In most injection molding cycles, it is necessary to adjust the amount of rotation of the screw village, so that when the screw is injected, most of the soft plastic will be left, which ensures that the screw reaches an effective advancement time and maintains a fixed firing pressure. The size of the small injection molding machine is about 3mm; the size of the large injection molding machine is 9mm. No matter how much screw padding value you use, it must remain the same. The size of the screw pad can now be controlled within 0.11 mm.